Abnormal or diseased biological tissues are often diagnosed and monitored with histopathology, for example, with histopathological assessment of a biopsy sample. The presence, concentration and distribution of biological molecules (such as nucleic acid, protein or lipids for example) or different portions and structures of the tissue can be determined by selecting a specific combination of chemical stains and fixatives. Visualization of the histological structures in a biological tissue sample is a basic procedure undertaken by a pathologist to reach a specific diagnosis on the disease that might have afflicted a patient, for example, kidney disease, liver disease, and the like. In particular, a pathologist assesses any variation in the morphological structures of the different components of the tissue, such as irregularities in shapes and sizes, and correlates the identified changes, if any, to a particular disease. Normally, a pathologist uses a physically stained tissue sample (a sample stained with a dye, for example) and relies on color cues to interpret texture and morphology of such tissue in arriving at his diagnosis. In comparison with an unstained tissue sample, in which histological structures are not clearly differentiated and which generally appears colorless when viewed under a microscope, a stained tissue specimen provides a clear illustration of the histological structures as well as vivid visual discrimination of the different tissue components. Various types of dyes are available to stain the tissue samples, each of the dyes labeling the histological structures with distinguishing colors thereby emphasizing the differences among such components. Choice of which type of stain to use depends mainly on what tissue structure is to be assessed in the diagnosis. Popular for routine staining are, for example, the hematoxylin and eosin (HE) dyes that facilitate differentiation between the nuclear region and the cytoplasm and connective tissues. Hematin (an oxidized form of hematoxylin) is a basophilic pigment having affinity to bound to a negatively-charged substance such as DNA of the cell's nucleus. As a result of treating the cell with hematoxylin, the cell's nucleus changes its color to purple-blue. Eosin, on the other hand, is an acidophilic pigment that binds to a positively-charged substance. Proteins contained in cytoplasm are colored in shades of red when stained with eosin.
A well-trained histopathologist can diagnose and grade the severity of a tissue disease based on color, shape, degree of staining, as well as pattern of a variety of stains. FIG. 1 illustrates schematically an example of the sequence of a conventionally-conducted pathological evaluation of a sample under test. In reference to FIG. 1, the initial diagnosis of the sample's condition is based on the evaluation of the HE-stained sample. As shown, the biological sample prepared at step 104 is subsequently stained with the HE dye at step 108. The staining procedure conventionally takes several days, depending on the available facilities (for example, Δt1 between 1 and 3 days). The pathologist then evaluates the HE-stained sample, at step 112, to provide an initial diagnosis that may indicate a problem such as the presence of a lesion, for example. Such “positive” finding of a problem, once made, may prompt, at step 116, that an additional evaluation be required to localize the indicated problem (for example, to localize the targeted lesion in the sample). In this case, a specimen of the same biological tissue is prepared, at step 120, by staining the specimen with a so-called “specific” stain. The specific stain (such as Masson's trichrome stain, or MT; Victoria blue stain, or VB; or Ciemsa stain, for example) is appropriately chosen to cause chemical reaction(s) with the specific component(s) or compounds of the cell (such as enzymes, polysaccharides, lipids, metals, and ions, for example) that facilitate(s) the localization of the targeted problematic substance. The preparation of a specifically-stained sample takes several days more. Consequently, another, final evaluation step 124—the evaluation of the specifically-stained sample—is carried out by a histopathologist several days (for example, Δt2=1 to 3 days) later, bringing with it, at step 128, a final diagnosis about the condition of the patient. However, if the additional evaluation is not required, the final diagnosis can be made, at step 132, on the basis of the initial evaluation.
It is appreciated, therefore, that the process of diagnosis of the patient's condition may require multiple days. The longer the overall time, Δt1+Δt2, needed to arrive at the final diagnosis (step 128), the more the patient is likely to be physically and mentally burdened. As the related art indicates, the desire to reduce the delay in diagnosis process prompted the preparation of both the HE-stained sample and the specifically-stained sample(s) ahead of the initial evaluation, and sometimes regardless of what specific staining may or may not be necessary. While by doing so the histopathologist has an option of using the required specifically-stained sample(s) immediately following the decision step 116, the anticipatory preparation of the specifically-stained sample(s) is problematic and costly as it leads to unnecessary waste of samples, staining effort, and time of the histopathology technician. Consequently, there remains a problem of reducing time required to arriving at the ultimate diagnosis of the condition of the specimen.